God's plan from eternity was that in Christ Jesus he would "make in himself of twain(Jews and Gentiles) one new man...that he might reconcile both unto God in one body by the cross, slaying the hostility that was between them"(Eph. 2:13-18) and thus build the household of God(Eph. 2:19-22), the Church, which is His Body, which is the fulness of Him that fills all in all(Eph. 1:23), "His intent was that now, through the church, the manifold wisdom of God should be made known to the rulers and authorities in the heavenly realms, according to his eternal purpose which he accomplished in Christ Jesus our Lord"(NIV, Eph. 3:10,11). It was God's plan to save us(Eph 2:8,9) so that we would be a part of His eternal plan of grace which He will reveal to us throughout the ages to come(Eph. 2:7); This Mystery, has been revealed to us(Eph. 3:1-6), St Paul preached, "among the gentiles the unsearchable riches of Christ, to make all men see what is the fellowship of the mystery, which from the beginning of the world has been hid in God, who created all things by Jesus Christ. We have redemption, forgiveness of sins(Eph. 1:7); we have an inheritance(Eph. 1:11); we are sealed by the Holy Spirit(Eph. 1:13); we have promise of future bodily redemption(Eph. 1:14); we have been blessed with ALL spiritual blessings in heavenly places in Christ(Eph.1:3); "There is one body!!!, and one Spirit!!!...one hope!!!...One Lord!!!, one faith!!!, one baptism!!!, One God and Father of all!!!"(Eph 4:1-6). God gave gifts to the Church "for the perfecting of the saints, for the work of the ministry, for the edifying of the body of Christ(Eph. 4:8-14). God chose a committed and Godly marriage as a picture of the relationship between Christ and His body, the Church(Eph.5:22-33); the Church is the very flesh of Christ, "For we are members of his body, of his flesh, and of his bones"(Eph. 5:30); "THIS IS A GREAT MYSTERY: but I speak concerning CHRIST AND THE CHURCH(Eph.5:32).
NOTE: Had the princes of this world known what the Mystery was they would not have crucified the Lord of Glory(1 Corinthians 2:6-8). "But we see Jesus, made a little lower than the angels by the suffering of death...bringing many sons unto glory"(Hebrews 2:9,10). St Paul was "made a minister, to fulfil the Word of God; even the mystery which has been hid from ages and from generations, but now is made manifest to his saints: to whom God would make known what is the riches of the glory of this mystery among the gentiles; which is Christ in you the hope of glory"(Colossians 1:25-27). "Now to him that is of power to establish you according to my gospel, and the preaching of Jesus Christ, according to the revelation of the mystery, which was kept secret since the world began, But now is made manifest, and by the scriptures of the prophets, according to the commandment of the everlasting God, made known to all nations for the obedience of faith: To God only wise, be glory through Jesus Christ for ever. Amen."(Romans 16:25-27)